• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.11
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• pp.1005-1012
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• 2011

In this paper, the effect of wrinkling on the failure behavior of thin membrane was studied using geometrically nonlinear shell element post-buckling analysis with global-local analysis strategy. In the analysis, double-edge notched and single-edge notched tensile specimen configurations were considered. The analyses were performed for both cases with allowing and suppressing the wrinkling deformation. The results were investigated focusing on the effect of wrinkle development on the variation of J-integral values at the cut tip. The effect of cut lengths and the specimen lengths were also systematically studied.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.141-144
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• 1984

The fatigue limits of crack initiation and propagation on the edge elliptical notched semi-infinite plate under completely reversed fatigue stress are determined theoretically. Assuming that the crack initiation and propagation occur when stress intensity factors of notched plate reach the critical values obtained from critical micro-crack length under plain fatigue limit loading and the threshold stress intensity factory, respectively, the fatigue limits of crack initiation and propagation are obtained. The induced theoretical fatigue limit of crack initiation is expressed in terms of plain fatigue limit, critical micro-crack length and notch shape. The one of crack propagation is in terms of threshold stress intensity factor, plain fatigue limit and notch shape. These theoretical results are showed to be in good agreement of Frost's experimental data.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.816-817
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• 2015

본 논문에서는 매입형 영구자석 전동기의 코깅토크 저감을 위해 회전자 표면에 노치를 적용하여 최적 설계를 수행하였다. 최적 설계를 위해 전역 최적점의 빠른 탐색이 가능한 크리깅 근사모델을 이용한 진화전략 알고리즘이 사용되었다. 설계 변수인 노치 크기에 대해 코깅 토크를 목적 함수로 두고 최적 설계를 진행하였으며, 이를 통해 찾은 전역 최적점과 지역 최적점 가운데 역기전력 특성을 고려하여 최종 설계안을 도출하였다.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.217.1-217
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• 2003

1. 3시간 침수시켜 분홰한 찹쌀가루를 20meshcp를 통과시켜 시료로 이용했다. 2. 찹쌀에 대한 엿기름의 첨가량과 처리시간을 달리하여 노치를 제조한 결과 5%엿기름 첨가로 8시간 삭히는 조건이 최대의 전체적인 맛을 나타냈다. 3, 엿기름의 처리온도는 5$0^{\circ}C$조가 6$0^{\circ}C$에서 총당과 환원당 함량이 높고 요오드 비색도 값은 작았다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1411-1417
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• 2010

CFRP (Carbon Fiber Reinforced Plastic) has received considerable attention in various fields as a structural material, because of its high specific strength, high specific stiffness, excellent design flexibility, favorable chemical properties, etc. Most products consisting of several parts are generally assembled by mechanical joining methods (using rivets, bolts, pins, etc.). Holes must be drilled in the parts to be joined, and the strength of the components subjected to static and fatigue loads caused by stress concentration must be decreased. In this study, we experimentally evaluated the variation in the residual strength of a holenotched CFRP plate subjected to fatigue load. We repeatedly subjected the hole-notched specimen to fatigue load for a certain number of cycles, and then we investigated the residual strength of the hole-notched specimen by performing the fracture test. From the results of the test, we can observe the initiation of a directional crack caused by the applied fatigue load. Further, we observed that the residual strength increases with a decrease in the notch effect due to this crack. It was evaluated that the residual strength increases to a certain level and subsequently decreases. This variation in the residual strength was represented by a simple equation by using a model of the decrease in residual strength for plain plate, which was developed by Reifsnider and a stress redistribution model for hole-notched plate, which was developed by Yip.

• Tunnel and Underground Space
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• v.9 no.1
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• pp.64-71
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• 1999

A numerical analysis was performed to investigate the effects of notched blasthole in controlling the fracture plane. Analyzed were elastic and elasto-plastic response of rock, and fracture propagation under static and dynamic load conditions. Results showed that the region exceeding the tensile strength extended up to three times the radius of a normal blasthole in elastic analysis, while fifteen times in elasto-plastic analysis. It was shown that a crack was driven from the notch tip up to the distance of 23 times the hole radius in the case of a notched blasthole with a notch of 5 mm in depth and 30 mm in length.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.2
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• pp.109-116
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• 2022

In this paper, we propose a band rejection filter (BRF) with a state variable filter (SVF) structure to effectively remove the influence of 60 Hz line frequency noise introduced into the sensor system. The conventional BRF of the SVF structure uses an additional operational amplifier (OPAMP) to add a low pass filter (LPF) output and a high pass filter (HPF) output or an input signal and a band pass filter. Therefore, the notch frequency and the notch depth that determine the signal attenuation of the BRF greatly depend on the tolerance of the resistors used to obtain the sum or difference of the signals. On the other hand, in the proposed BRF, since the BRF output is formed naturally within the SVF structure, there is no need for a combination between each port. The notch frequency of the proposed BRF is 59.99 Hz, and it can be confirmed that it is not affected at all by the tolerance of the resistor through the Monte Carlo simulation results. The notch depth also has an average of -42.54dB and a standard deviation of 0.63dB, confirming that normal operation as a BRF is possible. Also, with the proposed BRF, noise filtering was applied to the electrocardiogram (ECG) signal that interfered with 60 Hz noise, and it was confirmed that the 60 Hz noise was appropriately suppressed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.303-306
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• 2011

티타늄 용접부의 기공 형성은 용접 중 대기중으로부터 유입되거나 모재 표면의 산화막으로부터 확산과정을 통해 유입되는 산소 혹은 수소로 인해 형성된다고 알려져 있다. 용접부 기공은 용접부의 피로 수명과 인성을 저하시키며 취성 파괴의 원인이 된다. 이에 용접 후 비파괴 검사를 통해 용접부 기공을 확인하고 있으며 확인된 기공등의 결함은 재용접을 통해 제거하고 있다. 이번 연구에서는 기계적 가공 방법에 의해 기공을 제거한 후 재용접 하는 기존의 방식에서 벗어나 TIG Dressing 공법을 이용하여 용접부에 형성된 기공을 제거하고자 하였으며 이에 따른 용접부 노치 인성을 확인하였다. 시험 결과 TIG Dressing에 의한 기공 제거 효과와 노치 인성을 확인하였다.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.131-134
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• 2014

PMSM(Permanent Magnet Synchronous Motor)은 가공기, 로봇, 공장 자동화 등 현재까지도 산업 시스템 전반에 널리 쓰이고 있으며, 그에 대한 연구도 활발히 진행되고 있다. 하지만 PMSM에 부하를 인가하거나 혹은 기계 몸체와의 결합 과정에서 기구부가 가지고 있는 고유진동 주파수에 의해 동력 전달 부분에 있어 기계계의 응답 특성은 불안정해지고, 떨림 현상이 발생된다. 본 논문에서는 PMSM을 이용한 회전 운동 시스템에서 출력되는 전류에 기구부가 가지고 있는 특정 영역의 고유진동 주파수를 제거한 전류를 적응 노치필터를 통해 내보낸다. 그 결과 기계부의 떨림 현상을 제거하고, 안정적인 제어 시스템을 제안한다. 이 제어알고리즘을 가상실험으로 필터 통과 전과 후의 결과를 비교 및 분석하도록 한다.

• Composites Research
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• v.12 no.3
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• pp.26-35
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• 1999

The static strength and fatigue life of repaired graphite/epoxy laminates are observed using tensile coupon. The lay-up of investigated laminates was [$0^{\circ}$/$\pm$$45^{\circ}$/$90^{\circ}$]$_s$. Static strength was measured from the specimens prepared by various repair techniques such as precured-single patch, precured-double patch and cure-in-place methods. The strength was recovered to the extent of 60~80 % of unnotched case. Fatigue life was also measured from the laminates repaired with cure-in-place method. Hwang and Han's MFLPE 1(modified fatigue life prediction equation 1), which was based on the fatigue modulus degradation model and reference modulus, was chosen for fatigue life prediction of repaired specimen and compared with the conventional fatigue life equation such as S-N curve and Basquin's relation. The MFLPE 1 has better agreement with experimental data than S-N curve and Basquin's relation.